Novel Therapeutic Concepts in Targeting Glioma Edited by Faris Farassati potx

Contents Preface IX Part 1 Surgical Therapy of Glioma 1 Chapter 1 Innovative Surgical Management of Glioma 3 Dave Seecharan, Faris Farassati and Ania Pollack Part 2 EGFR and Glioma The

NOVEL THERAPEUTIC

CONCEPTS IN TARGETING GLIOMA

Edited by Faris Farassati

Novel Therapeutic Concepts in Targeting Glioma

Edited by Faris Farassati

As for readers, this license allows users to download, copy and build upon published chapters even for commercial purposes, as long as the author and publisher are properly credited, which ensures maximum dissemination and a wider impact of our publications

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First published April, 2012

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Novel Therapeutic Concepts in Targeting Glioma, Edited by Faris Farassati

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ISBN 978-953-51-0491-9

Contents

Preface IX Part 1 Surgical Therapy of Glioma 1

Chapter 1 Innovative Surgical Management of Glioma 3

Dave Seecharan, Faris Farassati and Ania Pollack

Part 2 EGFR and Glioma Therapy 25

Chapter 2 Advances in the Development of EGFR Targeted

Therapies for the Treatment of Glioblastoma 27 Terrance Johns

Chapter 3 Future Perspectives of Enhancing

the Therapeutic Efficacy of Epidermal Growth Factor Receptor Inhibition in Malignant Gliomas 43 Georg Karpel-Massler and Marc-Eric Halatsch

Part 3 MicroRNAs in Treatment of Glioma 57

Chapter 4 MicroRNA and Glial Tumors:

Tiny Relation with Great Potential 59

Jiri Sana, Marian Hajduch and

Ondrej Slaby

Chapter 5 The Role of microRNAs in Gliomas

and Their Potential Applications for Diagnosis and Treatment 75 Iris Lavon

Part 4 Inhibition of Invasion in Treatment of Glioma 89

Chapter 6 Molecular Targets:

Inhibition of Tumor Cell Invasion 91 Raquel Brandão Haga and Silvya Stuchi Maria-Engler

Part 5 Blood-Brain Barrier in Glioma Therapy 109

Chapter 7 Blood-Brain Barrier and Effectiveness

of Therapy Against Brain Tumors 111 Yadollah Omidi and Jaleh Barar

Part 6 Gene Therapy of Glioma 141

Chapter 8 Glioma-Parvovirus Interactions:

Molecular Insights and Therapeutic Potential 143

Jon Gil-Ranedo, Marina Mendiburu-Eliçabe,

Marta Izquierdo and José M Almendral

Chapter 9 The Potential and Challenges of siRNA-Based Targeted

Therapy for Treatment of Patients with Glioblastoma 161

M Verreault, S Yip, B Toyota and M.B Bally

Chapter 10 Hypoxia Responsive Vectors

Targeting Astrocytes in Glioma 199

Manas R Biswal, Howard M Prentice

and Janet C Blanks

Part 7 LGI1 in Treatment of Glioma 217

Chapter 11 The Tumor Suppressor Function of LGI1 219

Nadia Gabellini

Part 8 Antioxidant Adaptive Response in Glioma 245

Chapter 12 Antioxidant Adaptive Response of Malignant

Glioma Related to Resistance to Antitumor Treatment 247 Tomohiro Sawa and Takaaki Akaike

Part 9 TRP Channels in Glioma Therapy 263

Chapter 13 Ionic Channels in the Therapy of Malignant Glioma 265

Xia Ding, Hua He, Yicheng Lu and Yizheng Wang

Preface

Brain, the source of human’s ingenuity, passion, motivation and emotions holds a world of mystery and promises for scientists, biologists, physicians, philosophers and poets! It is, therefore, not surprising that Gliomas, as the most common form of the malignant brain tumors, impose such a strong impact on our society at different levels

Despite a series of significant improvements in our understanding about the molecular etiology of Gliomas, the road lays long in front of us to reach the ultimate goal of elimination of the burden delivered to human health by these deadly diseases But, in this mix, there are also good news: First, the rate of malignant brain tumors in men seems to be declining Secondly, the overall incidence rate of Glioblastomas has been stable suggesting that external risk factors may not influence the origination of these malignancies*

Novel Therapeutic Concepts for Targeting Glioma offers a comprehensive collection of

current information and the upcoming possibilities for designing new therapies for Glioma by an array of experts ranging from Cell Biologists to Oncologists and Neurosurgeons A variety of topics cover therapeutic strategies based on Cell Signaling, Gene Therapy, Drug Therapy and Surgical methods providing the reader with a unique opportunity to expand and advance his knowledge of the field

We remain grateful to the efforts of our colleagues at INTECH for providing such an

accessible and efficient platform for dissemination of science Our hopes are raised and our spirits are lifted because of endeavors of the people who not only seek but one day will deliver human race’s freedom from Cancer

Faris Farassati, PhD, PharmD,

Department of Medicine-Molecular Medicine Laboratory The University Of Kansas Medical Center, Kansas City, Kansas,

USA

*Kohler BA, Ward E, McCarthy BJ, Schymura MJ, Ries LAG, Eheman C, Jemal A, Anderson RA, Ajani

UA, Edwards BK Report to the Nation on the Status of Cancer, 1975-2007, Featuring Tumors of the Brain and Other Nervous System JNCI; May 4, 2011.

Surgical Therapy of Glioma

Innovative Surgical Management of Glioma

Dave Seecharan1, Faris Farassati1 and Ania Pollack2

2 Current surgical management of glioma

Three options are available for the surgical management of gliomas The first option is to refrain from surgery for as long as possible, sometimes referred to as the “wait and see” approach The second option involves biopsy of the lesion or subtotal resection of surgically accessible areas within the tumor in order to obtain histopathology diagnosis Biopsy and subtotal resection are often followed by adjuvant therapies (radiation or chemotherapy) The

best surgical option is gross total resection (GTR), usually defined as removal of all areas of contrast enhancement on T1 weighted MRI obtained postoperatively GTR provides the best surgical treatment and is associated with the best survival rates; however, it also carries the greatest risks of postoperative neurologic deficits and disability

Current treatment for glioma, particularly high grade lesions, is not curative and the majority of patients experience reoccurrence following initial resection Reoccurrence is due

to the infiltrative nature of these lesions and the inability of current treatment modalities to fully remove and destroy all tumor cells The rationale behind surgical management of these aggressive lesions is based on the Gompertzian phenomenon In 1825, the English mathematician Benjamin Gompertz postulated that the biological growth of normal organs and malignancies follows a characteristic curve and that cell number increases with time, but the relative rate of increase falls exponentially as the mass reaches a “plateau phase” of a very slow actual growth4 Therapy can induce regression in tumor volume, however, there

is always regrowth between cycles of treatment and this “regrowth” will follow the same Gompertzian growth curve The only escape from Gompertzian phenomenon is complete tumor cell eradication Therefore, the ultimate goal of surgical therapy in these tumors should

be the complete eradication of all abnormal neoplastic cells With the currently available surgical techniques we are still unable to fully resect most of these tumors Therefore we need new techniques to improve surgical resection as well as adjuvant therapies to eradicate remaining tumor cells and thereby maximize the survival benefit of surgery

Low grade gliomas (WHO I and II) are a broad group of tumors that are clinically, histologically and molecularly diverse WHO grade I tumors comprise the group of pilocytic astrocytoma and subependymal giant cell astrocytoma the more common being pilocytic Management of WHO grade I glioma consists of gross total resection as the treatment of choice and carries an excellent prognosis Following resection, 25-year survival rates of 50-94% have been reported5 Grade I lesions are the only glioma subtype where gross total resection is considered curative

WHO grade II gliomas consist of diffuse fibrillary astrocytoma, oligodendrogliomas, and oligoastrocytomas, all of which have similar invasive and malignant potential Grade II gliomas that are symptomatic and surgically accessible should undergo maximal cytoreductive surgery as the treatment of choice Predictors of incomplete tumor resection in low grade lesions include tumor involvement of the cortico-spinal tract, large tumor volume, and oligodendroglioma histopathologic type 5 year survival of up to 95-97% has been reported following gross total resection in these lesions6 In 2008, Smith and colleagues reported a large series of 216 patients with biologically aggressive grade II lesions and examined the extent of resection and the effect on overall survival7 Patients with at least 90% resection showed 5 and 8 year survivals of 97% and 91% respectively compared to those with less than 90% resection who showed survival rates of 76% and 60% at 5 and 8 years

For both grade I and grade II tumors, maximal surgical resection is the single best treatment for obtaining increased survival In cases where there is progressive tumor growth following resection or progressive neurological symptoms in unresectable tumors, adjuvant chemotherapy or radiation treatment may be used

High grade glioma’s (WHO III and IV) consist of anaplastic astrocytoma (Grade III), and glioblastoma (Grade IV) These tumors are malignant and carry a significantly poorer

prognosis than the low grade lesions The first line therapy for high-grade glioma is cytoreductive surgery with the goal of removing as much abnormal tissue as possible without causing further damage to normal parenchyma The reduction in tumor volume results in improved survival and quality of life by delaying recurrence and malignant progression

There are many studies over the past two decades that examine the extent of cytoreductive surgery; gross total resection verses biopsy and subtotal resection in regards to increasing patient survival Tumor location as well as extent of neurologic deficits plays a large role in the decision making process for surgical management One retrospective study in 1996 showed significant increased mean survival time of 292 days vs 184 days between a group undergoing cytoreductive surgery and a group undergoing stereotactic biopsy respectively8 However quality of life measured by KPS was not significantly different between the two groups

A prospective study utilizing 60 patients, examined the extent of resection compared to survival These authors found median survival of 64 weeks for the group who underwent gross total resection compared to 36 weeks for the group undergoing subtotal resection9 They concluded that patients undergoing subtotal resection have 6.6 times higher risk of death Another large prospective of study 645 patients showed that patients undergoing total resection had a median survival of 11.3 months compared to 10.4 months for subtotal resection, both of which were significant increases in survival compared to 6.6 months for patients with biopsy only10

Increased survival with resection holds true even for the elderly A study by Vuorienen, focusing specifically on elderly patients over the age of 65 showed median survival of 5.7 months with open craniotomy and surgical resection compared to 2.8 months with stereotactic biopsy alone for an increased estimated survival time of 2.7 times longer in the resection group11 However, this increased survival time is modest in this patient population providing only a 2-3 month survival benefit The role of aggressive surgical management in the elderly population is still a controversial subject Chronological age however, is not necessarily the most important factor to consider in deciding to pursue an aggressive surgical course Rather biological age which takes into account the patients general health and functional level should be used as a guideline

A recent review article from 2008 examined over thirty published articles from the neurosurgical and neuro-oncologic literature regarding extent of resection and the effects on survival for malignant glioma Only one study failed to support the idea that extent of surgical resection correlates with an increased survival advantage12 These authors recommend that based on the current prospective and retrospective data that for newly diagnosed malignant glioma in adults, maximal cytoreductive surgery should be undertaken provided that postoperative neurological deficits are minimized

Studies have also been performed in order to quantify exactly what percent of tumor resection is necessary to provide maximal survival benefit The original landmark study was published in 2001 by Lacroix and colleagues in which they performed a retrospective analysis of 416 patients with glioblastoma treated with surgical resection13 Patients who received resection of greater than 98% had a mean survival of 13 months compared to patients receiving resection of less than 98% with mean survival of 8.8 months

A more recent 2011 retrospective study by Sanai and colleagues also quantified the percent

of tumor resection required for maximal survival benefit14 500 patients with gliobastoma were treated with surgical resection followed by standard radiation and chemotherapy They found a survival benefit with extent of surgical resection of as low as 78% However, for maximal survival benefit, resection of greater than 95% was observed

Overall, these studies demonstrate that prolonged survival time correlates with the extent of surgical resection The data also suggests that for high grade lesions, resection of greater than 95% of the tumor volume should be performed in order to provide the maximal survival benefit In some cases, however, such a high level of resection is unable to be obtained This is usually due to tumor involvement in areas of eloquent brain tissue (areas involved with speech production, motor function and sensory perception), and is associated with a high risk of postoperative deficits Maximizing the extent of tumor resection while preserving normal brain function and optimizing quality of life postoperatively represents a major challenge in neurosurgery Several strategies and innovative techniques have been developed to assist the surgeon in safely resecting tumors located in these eloquent areas, particularly in the areas of neuroimaging, neuronavigation, functional mapping, and photodynamics Theses new developments provide for greater resection volumes and better survival rates

3 Neuronavigation

Image guided neuronavigation utilizes the principle of stereotaxis The brain is considered

as a geometric volume which can be divided by three imaginary intersecting spatial planes based on a Cartesian coordinate system Any point within the brain can be specified by measuring its distance along these three planes This provides a precise surgical guidance by referencing this coordinate system of the brain with a parallel coordinate system of the three-dimensional image data of the patient that is displayed on a computer-workstation so that the medical images become point-to-point maps of the corresponding actual locations within the brain15 Neuronavigation provides intraoperative orientation to the surgeon, helps in planning a precise surgical approach to the targeted lesion and defines the surrounding neurovascular structures Conventional neuronavigation typically utilizes a preoperative MRI which is registered to the patients skull at the beginning of the procedure and is used throughout the case without any update in imaging or reregistration of the imaging to the corresponding brain tissue Conventional neuronavigation is readily available at most centers providing neurosurgical care and is not particularly cost prohibitive (Figure 1)

Intraoperative MRI (iMRI) guided intracranial surgery improves upon the benefits of conventional stereotactic guided neurosurgery by providing a real time updated view of the anatomic relationship between tumor and normal brain structures During surgical resection utilizing traditional cranial neuronavigation, the brain parenchyma becomes distorted due

to changes in tumor volume, edema and volume of cerebrospinal fluid resulting in brain shift, which is not reflected in the preoperatively obtained MRI This results in less reliability

of the stereotactic guidance as the surgery progresses Intraoperatively obtained MRI allows updating of the images used for neuronavigation as well as updated visualization of the contrast enhancing tissue that remains

Fig 1 Neuronavigation Operating room setup with patient positioned and

neuronavigational stereotactic equipment (A) Neuronavigational MRI for stereotactic guided biopsy showing a temporal lobe glioma in three planes

Over the past decade several studies have looked at iMRI guided resection vs conventional neuronavigation in patients with glioma In 2000, Wirtz and colleagues examined 68 cases of high grade glioma resected with iMRI16 Of the 68 cases, 27% of showed GTR on the first iMRI scan and 66% percent underwent continued resection Median survival was 13.3 months for GTR vs 9.2 months for subtotal resection

In 2005, Hisrschberg and colleagues examined the use of iMRI in 32 patients with glioblastoma compared to a matched control group of 32 patients using conventional neuronavigation They found a mean survival time of 14.5 months in the iMRI group vs 12.1 months in the control group They also saw a significant increase in length of surgical time with iMRI 5.1 hours vs 3.4 with conventional navigation They also reported postoperative functional performance results, which were not significantly different between the two groups Neurologic improvement was seen in 16% of patients, 55% showed no change, and 19% showed some worsening of symptoms

In 2010, Senft and colleagues reported on 41 patients with glioblastoma, 10 of whom underwent resection with iMRI and 31 who received resection by conventional means17 GTR was seen in all 10 iMRI cases and 19 of the conventional group Median survival was 88 weeks for the iMRI group and 68 weeks for the conventional group Median survival in regards to the extent of resection was 74 weeks for the 29 patients who obtained GTR vs 46 weeks for the 12 patients who obtained subtotal resection

A recent 2011 review article of 12 studies from the current literature examined the benefits

of iMRI vs conventional stereotactic surgery for glioblastoma The authors concluded that iMRI guided surgery is more effective that conventional neuronavigational surgery in increasing the extent of resection and prolonging survival in patients with glioblastoma18 However there are currently no randomized trials with validated endpoints that demonstrate the additional value of iMRI guided surgery Intraoperative MRI is currently

of limited availability, adds significant expense and prolongs surgical time Therefore, the decision to use this modality should be made judiciously on a case by case basis

These systems are not perfect and continued improvements are needed Advances in real time surgical imaging are important to reduce the neuronavigational inaccuracies due to brain shift as well as to provide a clearer more accurate representation of the tumor margins throughout the case Currently these systems still rely heavily on a rigid fixation of the patient’s head and a registration landmark Movement of the patient’s head, pin slippage, and loss of registration can drastically limit the utility of these surgical tools and more robust technologies are needed Despite these limitations, the use of improved neuroimaging and newer methods of neuronavigation can significantly improve the extent

of resection and thereby increase the survival rates for patients with glioma

4 Functional mapping

Functional mapping is another tool that is changing the surgical management of glioma therapy These new techniques allow the protection of eloquent areas of the brain while permitting the extent of surgical resection to be maximized With this technology, lesions that were previously thought to be inoperable due to location are now often resectable One such procedure is awake craniotomy Intraoperative direct electrostimulation under awake

anesthesia is the best technique to locate eloquent domains as well as to distinguish functional area from nonfunctional area In 2008, Duffau and colleagues, reported the largest experience with cortical and subcortical mapping of gliomas affecting the language area19 They performed resection using awake craniotomy and direct electrical stimulation

in 115 patients 98% of patients improved or returned to their preoperative baseline following resection guided by direct electrostimulation Awake craniotomy however presents several challenges in regards to anesthesia, patient comfort and anxiety as well as

prolongation of operative time

Functional magnetic resonance imaging (fMRI) is another improving technology that shows promise for increasing the extent of surgical resection while minimizing neurological deficits by providing functional mapping with the use of newly developed imaging modalities The use of functional magnetic resonance imaging (fMRI) allows information regarding the location of specific brain functions such as speech, motor function, and sensory perception to be mapped to three-dimensional reconstructed MRI images Blood oxygen level dependent (BOLD) fMRI is one of the most commonly used forms of fMRI BOLDfMRI provides functional informationbased on cerebral hemodynamic responses by measuring changes in the ratio of blood oxyhemoglobin and deoxyhemoglobin during the presentationof a various stimuli to the patient This data can then be used to map task-driven regional cortical activity in patients to noninvasively locate the brains essential eloquent areas and guide surgical planning (Figure 2)

In 2010, Talacchi and colleges retrospectively examined the use of preoperative fMRI and neuronavigation compared to traditional intraoperative neurostimulation in 171 patients20 They found that preoperative fMRI provided equivalent rate of GTR when compared to the invasive neurostimulation 71% vs 73%c compared to 40% in resections not utilizing either modality Similar findings have been demonstrated by additional authors21,22 Together these studies support fMRI as a viable alternative to awake craniotomy and functional neurostimulation with the benefit of reduced operative time as well as elimination of the challenges associated with awake craniotomy

Diffusion tensor imaging (DTI) is an additional form of functional magnetic resonance imaging used to delineate white matter anatomy DTI is based upon the principle that water preferentially diffuses along the long axis of white matter tracts and the degree and direction of water diffusion can be measured Tractography uses algorithms to process this data and to reconstruct three-dimensional maps representing subcortical fiber tracts23 Tractography can be used in surgical planning to show the relationship between white matter tracts and tumor It can reveal whether tracts are displaced, disrupted, or infiltrated

by tumor (Figure 3)

In 2007, Wu and colleges reported a large prospective randomized controlled trial of 238 patients with gliomas24 A randomized study group of 118 patients underwent resection with DTI tractography and neuronavigation while a control group of 120 patients underwent resection with neuronavigation alone They found a significant increase in the ability to achieve GTR with the use of DTI tractography with 74.4 % of patients in the study group achieving GTR compared to 33.3% of patients in the control group This translated into an increased mean survival time 21.2 months in the study group compared to 14.0 months mean survival in the control group They also found better outcomes with DTI

tractography with motor strength deterioration occurring in 15.3% of patients in the study group compared to 32.8% in the control group Improved outcome was also demonstrated

in 6 month Karnofsky Performace Scale scores with a mean score of 77 for study group patients and 53 for the control group When combined, fMRI, neuronavigation, and DTI allows precise surgical resection of the maximal tumor volume while sparing intact fiber tracts as well as eloquent areas of the brain This results increased patient survival and improved functional outcomes

Fig 2 Functional MRI MRI generated from BOLD data in a patient with large frontal lobe glioma showing areas of activation during a sentence completion task

Fig 3 Tractography 3-Dimensional reconstruction showing fiber tracts generated from DTI MRI sequence in a patient with large glioblastoma multiforme

5 Florescence guided resection

Another problem arises in surgery when dealing with the infiltrating malignant cells present

at the tumor margins These cells often lie outside the area of enhancement on neuroimaging and intraoperatively appear grossly and microscopically indistinguishable from normal brain tissue These areas of infiltrating cells contribute to reoccurrence and negatively effect long-term tumor control if not resected

Fluorescence image guided surgical resection (FIGS) is another innovative surgical technique which uses fluorescence intraoperatively to enhance the visualization of abnormal tumor cells intraoperatively and allow for maximal extent of resection 5-Aminolevulinic acid (ALA) is injected systemically prior to surgery High grade gliomas and other metabolically active tumors take up ALA at a rapid rate After gross resection of the visible tumor, a specially filtered blue light can illuminate the areas of high uptake within the cavity allowing selective resection of the residual areas25

In 2000, Stummer and colleagues reported an initial study of the efficacy of FIGS which demonstrated FIGS to be quite specific (only 0.4 % of fluorescent biopsy sites did not contain tumor cells) and quite sensitive (81.6% of fluorescent biopsy sites contained tumor cells)26 In

2006 this same author reported a multicenter phase III trial comparing FIGS to placebo and found 64% complete surgical excision with fluorescence guided resection compared to 38%

complete excision in the placebo group27 In 2007 Stepp and colleagues reported similar findings with GTR in 65% of patients undergoing FIGS compared to 36% in placebo group28 They also demonstrated improved 6 month progression free survival in 41% of patients in the study group vs 21% in the control group

Despite the positive initial results with FIGS, there are several limitations of this modality The blue light used to illuminate 5-ALA has a depth of penetration of only a few millimeters and is easily obscured by blood products Also 5-ALA has minimal uptake in tumors that have minimal contrast enhancement or that do not enhance at all, such as low grade glioma29,30 Advances in florescence guidance, particularly in its use for resection of these low grade, non-enhancing lesions are needed As this technology continues to progress it will allow for greater extent of resection and increased survival in patients with glioma

6 Photodynamic treatment

Photodynamic treatment (PDT) is another novel surgical method for the treatment of malignant glioblastoma It utilizes the selective uptake of a photosensitizer by the individual tumor cells followed by irradiation of the tumor with light of a specific wavelength during surgery, which activates the photosensitizer to destroy the tumor cells selectively via oxidative reactions Many different photosensitisers have been studied with the most promising being haematoporphyrin derivative (HPD) One of the greatest benefits with PDT

is that it is a localized treatment, which lacks the systemic side effects associated with chemotherapy and radiation The major side effect associated with PTD is cerebral edema in the irradiated area which can usually be managed with steroids

In 2005, Stylli and colleagues reported one of the largest series of PDT for high grade glioma

in 136 patients31 They utilized HPD administered IV preoperatively followed by irradiation with laser light during surgery Median survival time following treatment for the 78 patients with glioblastoma was 14.3 months and median survival for the patients with anaplastic astrocytoma was 76.5 months The same authors have also reported a review of the literature examining 10 studies, which show similar results although with fewer numbers of patients32 They conclude that PDT shows potential as a novel adjuvant therapy for glioma treatment along with chemotherapy and radiation therapy However, further controlled clinical trials are needed to standardize HPD dosage as well as type and dose of light irradiation

7 Radiation therapy

Following surgical resection, radiation therapy (RT) is considered the next step in the treatment of glioma The principal goal of RT is to destroy residual tumor cells that were not removed with surgery, therefore preventing or postponing tumor reoccurrence RT is most affective on smaller lesions and is therefore an adjuvant therapy in addition to surgical resection Resection of maximal tumor bulk results in smaller residual volumes which are more responsive to RT and thereby increase the efficacy of RT Historically, conventional radiation therapy using external beam radiation has been the main modality of radiotherapy used for glioma Due to the risk of radiation induced injury to normal brain tissue, conventional radiation therapy is fractionated and the total dose is delivered over several treatments Standard therapy usually consists of a total radiation dose in the range of 50–60

Gy administered over 20-30 fractions each with a dose of 1.8–2.0 Gy 33

Novel methods of administering radiation therapy are also being developed Following optimal surgical resection, image guided stereotactic radiosurgery (SRS) is now being evaluated for treatment these lesions This new modality utilizes a single high doses of radiation specifically targeted to a well-defined lesions using detailed neuroimaging This allows delivery of focused radiation to the tumor with a much lower dose to adjacent non-targeted tissue which results in reduced side effects compared with traditional methods For low grade gliomas, adjuvant RT following resection has failed to show a survival benefit In cases of disease progression or inoperable lesions with neurologic symptoms, delayed RT appears to provide the same survival advantage as postoperative RT34 For newly diagnosed high grade gliomas studies have demonstrated that SRS does not provide

a significant survival advantage over conventional radiotherapy35,36 The use of SRS has also been explored as a treatment for recurrent high grade lesions A recent article by Romanelli and colleagues reviewed 17 retrospective studies examining the role of SRS in the treatment

of recurrent high grade glioma This review demonstrated that SRS is associated with prolonged survival in patients with recurrent GBM with median survival times ranging from 7.5 to 30 months37 SRS has been shown to have no significant advantage as a first line radiation therapy for glioma and the results for recurrent glioma are inconclusive, therefore further study on the role of SRS in glioma treatment is needed

In addition to externally administered sources of radiation therapy, interstitial brachytherapy is another form of radiation therapy used to treat glioma, which refers to surgical placement of the radioactive source a short distance from or within the tumor being treated Brachytherapy was developed due to the observation that 80% of malignant gliomas reoccur within 2cm of the initial tumor site following resection By placing the radioactive source directly in the tumor or tumor bed, continuous high dose radiation increases damage

to nearby proliferating tumor cells located at the margin with a rapid fall off in the dose delivered to normal cells which are located farther from the source

There are multiple surgical methods for delivering the radiation source to the tumor During surgery, temporary implants can be placed which provide a source of radiation for a specified duration and are then removed at a later time, however this usually requires multiple procedures To avoid multiple procedures, small radioactive seed have been developed which are surgically implanted and are left permanently to gradually decay over

a period of weeks to months to a state of zero radiation emission Another novel approach uses a surgically implanted catheter system with an expandable balloon reservoir implanted

at the site of resection and a catheter connecting to a subcutaneous access port A radioactive solution can then be injected percutaneously into the implanted reservoir and retrieved at a later time The most commonly radiation sources used for glioma brachytherapy are iodine-

125 and iridium-192

Brachytherapy is usually reserved for cases of high grade gliomas which have shown reoccurrence since several studies have shown no significant survival benefit for brachytherapy in newly diagnosed glioma38,39 One large randomized study by Selker and colleagues with 270 patients examined the use of interstitial brachytherapy in newly diagnosed high grade glioma40 Patients were randomized to two groups, one receiving resection, external beam radiation, and chemotherapy with the other group receiving resection, external beam radiation, chemotherapy, and 125I permanent interstitial

brachytherapy They found no statistical difference in the median survival time between the two groups for newly diagnosed high grade glioma

The results for brachytherapy in the case of recurrent high grade glioma appear to show improved survival41–43 One large study with 95 patients by Gabayan and colleagues examined the use of the GliaSite Radiation Therapy System in the treatment of recurrent high grade glioma This system utilizes 125I administered via a surgically implanted balloon catheter system All patient were initially treated with resection followed by external beam radiation Following reoccurrence, patients underwent maximal surgical debulking followed by implantation of an expandable balloon catheter system Radioactive solution was then administered between 2-6 weeks following the debulking procedure Patient undergoing this treatment showed median survival of 36.3 weeks from the time of the debulking surgery with a 1 year survival of 31.1% Although no control group was used in this study, survival times were compared to matched patients from another published study matched for age, KPS, and surgical management These control patients showed a median survival of 23 weeks following resection for reoccurrence The results from the brachytherapy group compare favorably with the control group Further studies including randomized trials are still needed but brachytherapy appears to show promise as adjuvant therapy in recurrent glioma

8 Chemotherapy

In addition to surgical resection and radiation therapy the other mainstay of treatment for malignant glioma is chemotherapeutics Chemotherapy is another adjuvant therapy to be utilized along with surgical resection As with radiation therapy, chemotherapy is more effective in treating smaller tumor volumes and therefore maximizing the extent of surgical resection is important in order to provide a more favorable response to chemotherapy44 Two main classes of drugs are currently used, alkylating agents (carmusitine, temozolomide) and antiangiogenic agents (bevacizumab)

9 Blood brain barrier

The blood brain barrier (BBB) presents difficulty in the chemotherapuetic treatment of gliomas as many agents that are effective for the treatment of systemic disease are unable to cross the BBB There have been several developments designed to open the BBB and provide direct treatment of the central nervous system Initial therapies to open the BBB made use of small lipophilic molecule drugs administered systemically for increased permeation across the BBB This approach was limited by drug binding to plasma protein as well as extravasation of the drug back across the BBB into the systemic circulation Other early treatments used osmotic modification of the BBB with agents such as mannitol given intra-arterially to disrupt the BBB followed by the chemotherapeutic agent of choice The effectiveness of these early methods were limited due to the transient elevation of drug concentration within the brain tissues and short drug half–life which did not allow for accumulation of the drug at a therapeutic concentration Over the past decade, several innovative surgical methods of opening the BBB have been developed to provide longer acting and direct treatment to the tumor cells

10 Implantable polymers

One advancement has come in the area of surgically implantable polymers, which are infused with chemotherapeutic agents These polymers are then placed into the surgical cavity following resection to provide direct application of the chemotherapeutic agent to the tumor bed over a prolonged period of time as the polymer degrades and releases the agent The most widely studied therapy of this nature utilizes a polyanhydride wafer embedded with carmustine (gliadel wafers) Gliadel is currently the only interstitial chemotherapy treatment approved for use with malignant glioma Wafers can be implanted at the time of initial surgery or reserved for episodes of reoccurrence Several trials have demonstrated increased survival following the use of implantable wafers For initial tumor treatment, increased survival has been shown of 13.9 months compared to 11.6 months in non-treatment group Wafer usage for treatment of tumor reoccurrence provided increased survival of 31 weeks compared to 23 weeks in non-treated patients45–47

Overall, these studies show a 35% risk reduction of death with the use of gliadel, with a median survival of 14 months, which is a 2.5 month improvement over placebo 1 year survival is approximately 10% better with use of gliadel48 Care must be taken with the use

of this therapy as side effects of necrosis, cerebral edema, and seizure are common but can

be controlled with steroid and antiepliptic therapy

Use of gliadel can also exclude from further clinical trials and newer treatments It can cause confounding effects on another trial because all of these are so new Improvement of surgical resection can eliminate these problems

Nanoparticles can be administered intravascularly or directly into the brain via a surgically implanted catheter Delivery of nanoparticles via surgically implanted catheter has the benefit of greater volume of distribution directly to the brain tissue compared with diffusion alone50 Development of these nanoparticle systems for treatment of malignant brain tumors

is currently in the animal model phase and no human studies are currently available Rat models of glioblastoma have shown increased survival using doxorubicin bonded to cyanoacrylate nanoparticles for delivery to tumor cells The drug transport across the BBB

by nanoparticles appears to be due to a receptor-mediated interaction with the brain capillary endothelial cells, which is facilitated by certain plasma apolipoproteins adsorbed

by nanoparticles in the blood Nanoparticle uptake appears selective to tumor cells in these models as the animals did not manifest signs of neurotoicity51

In addition to drug delivery, nanoparticles are being investigated for use in neuroimaging Current imaging techniques have a maximum resolution of 1 mm Nanoparticles could

improve the resolution by a factor of ten or more, allowing detection of smaller tumors and more precise surgical resection Several nanoparticle-based contrast materials have been used to enhance MRI imaging One iron oxide nanoparticle currently under study has shown an innocuous toxicity profile as well as sustained retention in mouse tumors52 These fluorescent nanoparticles improved the contrast between the tumor tissue and the normal tissue in both MRI and optical imaging, which can be used during surgery to see the tumor boundary more precisely

Another promising role of nanoparticle in the treatment of glioma involves hyperthermia treatment The heating of cancerous tissues between 41 and 45°C, has been shown to improve the efficacy of cancer therapy when used in conjunction with chemotherapy and radiation52 Magnetic nanocomposites based on iron oxide can be used as implantable biomaterials for thermal cancer therapy applications at the time of surgery These implanted particles can then be remotely heated by exposure to an external alternating magnetic field

In 2011, Maier-Hauff and colleagues reported a trial of magnetic nanoparticle thermotherapy

in conjunction with radiation treatments in 59 patients with recurrent glioblastoma53 Magnetic fluid was instilled within the tumor site using a neuronavigational procedure comparable to a brain needle biopsy and an external magnetic field was then applied for multiple treatments Patients undergoing this procedure showed a mean survival time of 13.4 months after the first re-occurrence Thermotherapy using magnetic nanoparticles in conjunction with a reduced radiation dose is safe and effective and leads to longer overall survival compared with conventional therapies in the treatment of recurrent GBM

12 Immunotherapies

Using the body’s own immune system to fight glioma, immunotherapy, is a new field which has seen significant advancements over the past decade There are two categories of immunotherapy for glioma that are currently undergoing clinical research Passive immunotherapy involves the activation of cytotoxic effector cells ex vivo and thee transfer of these activated cells back into the patient’s body Active immunotherapy, on the other hand, uses an exogenous trigger which causes activation of endogenous effector cells within the patients own body to target tumor cells Active immunotherapy is generally employed in the tumor vaccine model Surgery plays a large role in these therapies, as sizeable volumes

of tumor tissue must be surgically obtained in order to construct the immunotherapeutic agents Also several of these therapies utilize direct delivery of these agents into the brain during surgery

Current clinical trials utilizing passive immunotherapy focus on the activation of effector cytotoxic T lymphocytes, natural killer cells, or lymphokine activated killer cells sensitized

to glioma-associated antigens Once such trial for glioblastoma treatment uses donor cytotoxic T lymphoyctes which are sensitized ex vivo to recognize patient human leukocyte antigen (HLA) groups expressed on the surface of glioma cells but not on normal neurons or glia After surgical resection, the sensitized CTL cells are placed in the resection cavity as well as surgical placement of an intraparanchemal catheter and reservoir system to allow future delivery of CTL cells An initial pilot study with this model showed significant survival benefit in 3 of 6 patients with 2 patients surviving >15 years since beginning immunotherapy54

Treatments using active immunotherapy via cell-based and peptide vaccines are also under study Cells from glioma tumors are thought to be poor antigen-presenting cells because they often secrete immunosuppressive cytokines as well as growth factors such as transforming growth factor and vascular endothelial growth factor which can have a negative effect on T cell and natural killer cell activity Tumor vaccines are designed to augment tumor-specific cellular immunity and enhance low-level immunity by stimulating the production of higher-avidity T cells specific to a tumor55.

Chang and colleagues published results from one vaccine based phase II clinical trial in

2011 16 patients with glioblastoma (8 newly diagnosed, 8 recurrent) underwent craniotomy for maximal cytoreduction followed by standard external beam radiation therapy in the newly diagnosed patients Tumor cells obtained from the surgical resection were cultured

in the laboratory and combined with autologous dendritic cells to produce vaccine The vaccine was administered to patients via subcutaneous injection over lymph nodes for a total of 10 treatments over a 6 month period Median survival and 5 year survival was 381 days and 12.5% for the newly diagnosed group, 966 days and 25% for the recurrent group compared to 380 days mean survival and 0% five years survival for a 16 patient age and sex matched historical control group

Although most published results are from preliminary studies with small numbers of patients, immunotherapy for the treatment of glioma is a promising area currently undergoing multiple phase II and phase III trials for FDA approval54 Once the basic efficacy of these initial studies have been verified as a plausible modality for the treatment

of glioma, randomized and controlled clinical trials can be undertaken to further explore the full potential of this therapy

13 Gene therapy

Gene therapy is another novel modality used in the treatment of glioma, which focuses on the delivery of apoptotic genes at the time of surgical intervention and implantation in the surgical cavity One of the most effective methods of in vivo gene delivery is the use of viral vectors as gene carriers Retroviruses, adenovirus, and herpes simplex virus-1 (HSV-1) are all currently undergoing trials as vectors for viral brain tumor therapy Replication competent retroviruses have been shown to have infection rates of 97% with specificity for tumor cells without significant effects on non-tumor cells56 Adenovirus and HSV-1 are used

in both replication competent and replication defective forms and have shown high transgenic capacity and persistent gene expression57

In 2003, Germano and colleagues reported a series of 11 patients with high grade glioma treated with gene therapy using adenovirus as a viral vector57 Adenovirus was used to transfer the herpes simplex-thymidine kinase gene into malignant glioma cells This gene then phosphorylates ganciclovir, a non-cytotoxic nucleotide analog, into a compound that halts the transcription of DNA in dividing cells Since normal brain cells are not rapidly dividing they are not affected At the time of surgery, following gross total resection, the viral solution was injected directly into the tumor bed This was followed by administration

of ganciclovir systemically over 7 days Of the 11 patients 10 had a survival of > 52 weeks following treatment This survival time was associated with maintaining quality of life 8 patients maintained a KPS of greater than 70 after 3 months and 5 patients 6 months after treatment

Oncolytic viruses are also currently being used for clinical trials These virus replicate selectively within tumor cells and can lead to increased intratumoral viral titers and cell death58 In 2004, Harrow and colleges used a modified herpes simplex virus with an affinity for glioblastoma cells which replicates only in rapidly diving cells causing cell lysis while sparing normal terminally differentiated cells Twelve patients, 6 with newly diagnosed glioblastoma and 6 with recurrent glioblastoma, underwent craniotomy and surgical resection Following resection during the same surgical procedure they were injected with the modified herpes virus at 8-10 sights adjacent to the tumor bed Four patients, 2 newly diagnosed and 2 with recurrent disease showed survival of greater than 15 months following treatment

Viral vectors, although promising, do have several limitations Viral vectors suffer from low levels of gene incorporation due to limited diffusion into the brain parenchyma as well as low transfection rates of some cell types Formation of antigenicity to vectors and introduced gene products causes additional difficulties Also the use of retroviruses that incorporate genes into the host chromosome can result in insertional mutagenesis and propensity to form new tumors The use of genetically modified cells to deliver gene therapy to the CNS may avoid some of these limitations The use of stem cells is one area of research being used to avoid these limitations seen with traditional gene therapy

Neural stem cells (NSC) are self-renewing multipotent cells found in the fetal brain within the ventricular zone, midbrain and spinal cord These cells have the ability to repopulate a degenerated CNS region and can migrate toward pathologically altered tissues, including stroke, trauma and tumors Genetic changes in NSCs may result in tumorigenesis by activation of oncogenes and/or inactivation of tumor suppressor genes

Within brain tumors, a population of cells known brain tumor stem cells (BTSC) have been found They are resistant to current treatments and capable of maintaining and propagating these tumors59 BTSCs are thought to arise from aberrant NSCs or from mature cells that have undergone mutation and dedifferentiation BTSCs are similar to normal stem cells with regards to self-renewal, capacity, multi-potentiality, tumorigenicity as well as migratory capability Transformation of these neural stem cells and their progenitor cells may therefore lead to the formation of BTSCs and eventually malignancy60 Gene therapies focusing on preventing the malignant transformation of

NSCs into BTSCs as well as the use of normal stem cells as a method of targeted delivery of therapeutic agents to glioma cells are currently under investigation

Genetic modification of NSCs to secrete anti-tumor agents allows targeted delivery as well

as provides a high level of active compounds at the local site of neoplasm These types of therapies are still in the early stages and have not been evaluated in human glioma patients, however there are studies which have shown good results using animal models One model using neural stem cells modified to produce high quantities of interleukin-4 in vivo was examined in Spraque-Dawley rats61 They implanted the modified NSCs into the brain tissue

of rats affected with malignant gliobastoma and found a long term survival of 50% compared to control animals

Another rat study used immortalized neural progenitor stem cells to express a eukaryotic catalytic enzyme that converts the nontoxic compound 5-flourocytosine into the highly toxic

drug 5-flourouracil62 These stem cells were then implanted in rats with induced glioblastoma and the animals were subsequently treated with the nontoxic compound After

10 days, the animals treated with the modified NSCs showed significant 50% decrease in tumoral mass compared to a control group After histopathological examination of the treated tissue, they also found high levels of the toxic 5-flourouracil drug in adjacent tissue demonstrating in vivo conversion of the nontoxic compound to the toxic drug with therapeutic benefit

Neural stem cells are also being used as vehicles for the tracking and suppression of glioblastoma These methods exploit the tendency of NSCs to preferentially migrate towards brain tumors This allows NSCs to be labeled and used as diagnostic imaging tools to identify extent of tumor invasion One such animal model used NSCs modified to express the firefly luciferase gene63 These cells were then implanted into the contralateral brain parenchyma as well as injected into the ventricles of mice with intracranial gliomas Over a period of 3 weeks, serial bioluminescence imaging was performed, which showed migration

of the implanted cell across the corpus callosum with a maximal density at the site of the tumors A subsequent study using the same model but with the addition of an apoptosis-promoting gene to the NSCs was performed to evaluate the therapeutic possibilities of this model NSCs were modified not only to express the luciferase gene but also the tumor necrosis factor related apoptosis inducing ligand S-TRAIL The transformed NSCs were then stereotactically implanted into the left frontal lobe of mice and glioma cells were stereotactically injected into the right frontal lobe of the same animals Serial imaging was again performed which initially showed increased tumor volumes at the site of glioma injection as well as migration of the NSCs towards the tumor areas After 16 days however there was a considerable decrease in tumor growth and a significant reduction in tumor cells

on quantitative analysis compared to control animals They also found expression of the TRAIL gene product at the tumor site on histopathological examination These studies demonstrate the promising role that stem cells can play in the treatment of glioma

S-14 Conclusion

Surgical resection remains the single most important primary treatment in the management

of patients with glioma and extent of surgical resection directly correlates with increased patient survival In this chapter we reviewed several innovative technologies and surgical methods for increasing the extent of resection as well as several adjuvant therapies and the important role that surgery plays in maximizing the potential benefit of these therapies in the treatment of glioma As our ability to increase the extent of resection improves and new innovative technologies are perfected, we will continue to see improvements in long term survival in patients affected with glioma

[3] CBTRUS CBTRUS Statistical Report:Primary Brain and Central Nervous System Tumors

Diagnosed in the United States in 2004-2007 2011 Available at:

http://www.cbtrus.org/

[4] Norton L Conceptual and practical implications of breast tissue geometry: toward a

more effective, less toxic therapy Oncologist 2005;10(6):370-381

[5] Piepmeier J, Baehring JM Surgical resection for patients with benign primary brain

tumors and low grade gliomas J Neurooncol 2004;69(1-3):55-65

[6] McGirt MJ, Chaichana KL, Attenello FJ, et al Extent of surgical resection is

independently associated with survival in patients with hemispheric

infiltrating low-grade gliomas Neurosurgery 2008;63(4):700-707; author reply

707-708

[7] Smith JS, Chang EF, Lamborn KR, et al Role of extent of resection in the long-term

outcome of low-grade hemispheric gliomas J Clin Oncol 2008;26(8):1338-1345

[8] Kiwit JC, Floeth FW, Bock WJ Survival in malignant glioma: analysis of prognostic

factors with special regard to cytoreductive surgery Zentralbl Neurochir

1996;57(2):76-88

[9] Albert FK, Forsting M, Sartor K, Adams HP, Kunze S Early postoperative magnetic

resonance imaging after resection of malignant glioma: objective evaluation of

residual tumor and its influence on regrowth and prognosis Neurosurgery

1994;34(1):45-60; discussion 60-61

[10] Simpson JR, Horton J, Scott C, et al Influence of location and extent of surgical

resection on survival of patients with glioblastoma multiforme: results of three

consecutive Radiation Therapy Oncology Group (RTOG) clinical trials Int J Radiat Oncol Biol Phys 1993;26(2):239-244

[11] Vuorinen V, Hinkka S, Färkkilä M, Jääskeläinen J Debulking or biopsy of malignant

glioma in elderly people - a randomised study Acta Neurochir (Wien)

2003;145(1):5-10

[12] Ryken TC, Frankel B, Julien T, Olson JJ Surgical management of newly diagnosed

glioblastoma in adults: role of cytoreductive surgery J Neurooncol

2008;89(3):271-286

[13] Lacroix M, Abi-Said D, Fourney DR, et al A multivariate analysis of 416 patients with

glioblastoma multiforme: prognosis, extent of resection, and survival J Neurosurg

2001;95(2):190-198

[14] Sanai N, Polley M-Y, McDermott MW, Parsa AT, Berger MS An extent of resection

threshold for newly diagnosed glioblastomas J Neurosurg 2011;115(1):3-8

[15] Ganslandt O, Behari S, Gralla J, Fahlbusch R, Nimsky C Neuronavigation: concept,

techniques and applications Neurol India 2002;50(3):244-255

[16] Wirtz CR, Knauth M, Staubert A, et al Clinical evaluation and follow-up results for

intraoperative magnetic resonance imaging in neurosurgery Neurosurgery

2000;46(5):1112-1120; discussion 1120-1122

[17] Senft C, Franz K, Blasel S, et al Influence of iMRI-guidance on the extent of resection

and survival of patients with glioblastoma multiforme Technol Cancer Res Treat

2010;9(4):339-346

[18] Kubben PL, Ter Meulen KJ, Schijns OE, et al Intraoperative MRI-guided resection

of glioblastoma multiforme: a systematic review Lancet Oncol 2011 Available

at:

http://www.ncbi.nlm.nih.gov/pubmed/21868286 Accessed September 6, 2011 [19] Duffau H, Peggy Gatignol ST, Mandonnet E, Capelle L, Taillandier L Intraoperative

subcortical stimulation mapping of language pathways in a consecutive series of

115 patients with Grade II glioma in the left dominant hemisphere J Neurosurg

2008;109(3):461-471

[20] Talacchi A, Turazzi S, Locatelli F, et al Surgical treatment of high-grade gliomas in

motor areas The impact of different supportive technologies: a 171-patient series J Neurooncol 2010;100(3):417-426

[21] Leclercq D, Duffau H, Delmaire C, et al Comparison of diffusion tensor imaging

tractography of language tracts and intraoperative subcortical stimulations J Neurosurg 2010;112(3):503-511

[22] Roux F-E, Boulanouar K, Lotterie J-A, et al Language functional magnetic

resonance imaging in preoperative assessment of language areas: correlation

with direct cortical stimulation Neurosurgery 2003;52(6):1335-1345; discussion

1345-1347

[23] Awasthi R, Verma SK, Haris M, et al Comparative evaluation of dynamic

contrast-enhanced perfusion with diffusion tensor imaging metrics in assessment of

corticospinal tract infiltration in malignant glioma J Comput Assist Tomogr

2010;34(1):82-88

[24] Wu J-S, Zhou L-F, Tang W-J, et al Clinical evaluation and follow-up outcome of

diffusion tensor imaging-based functional neuronavigation: a prospective,

controlled study in patients with gliomas involving pyramidal tracts Neurosurgery

2007;61(5):935-948; discussion 948-949

[25] Eljamel S Photodynamic applications in brain tumors: A comprehensive review of the

literature Photodiagnosis and Photodynamic Therapy 2010;7(2):76–85

[26] Stummer W, Novotny A, Stepp H, et al Fluorescence-guided resection of glioblastoma

multiforme by using 5-aminolevulinic acid-induced porphyrins: a prospective

study in 52 consecutive patients J Neurosurg 2000;93(6):1003-1013

[27] Stummer W, Pichlmeier U, Meinel T, et al Fluorescence-guided surgery with

5-aminolevulinic acid for resection of malignant glioma: a randomised controlled

multicentre phase III trial Lancet Oncol 2006;7(5):392-401

[28] Stepp H, Beck T, Pongratz T, et al ALA and malignant glioma: fluorescence-guided

resection and photodynamic treatment J Environ Pathol Toxicol Oncol

2007;26(2):157-164

[29] Widhalm G, Wolfsberger S, Minchev G, et al 5-Aminolevulinic acid is a promising

marker for detection of anaplastic foci in diffusely infiltrating gliomas with

nonsignificant contrast enhancement Cancer 2010;116(6):1545-1552

[30] Floeth FW, Sabel M, Ewelt C, et al Comparison of (18)F-FET PET and 5-ALA

fluorescence in cerebral gliomas Eur J Nucl Med Mol Imaging

2011;38(4):731-741

[31] Stylli SS, Kaye AH, MacGregor L, Howes M, Rajendra P Photodynamic therapy of

high grade glioma - long term survival J Clin Neurosci 2005;12(4):389-398

[32] Stylli SS, Kaye AH Photodynamic therapy of cerebral glioma - a review Part II -

clinical studies J Clin Neurosci 2006;13(7):709-717

[33] Laperriere N, Zuraw L, Cairncross G Radiotherapy for newly diagnosed malignant

glioma in adults: a systematic review Radiother Oncol 2002;64(3):259-273

[34] Mirimanoff RO, Stupp R Radiotherapy in low-grade gliomas: Cons Semin Oncol

2003;30(6 Suppl 19):34-38

[35] Souhami L, Seiferheld W, Brachman D, et al Randomized comparison of stereotactic

radiosurgery followed by conventional radiotherapy with carmustine to conventional radiotherapy with carmustine for patients with glioblastoma

multiforme: report of Radiation Therapy Oncology Group 93-05 protocol Int J Radiat Oncol Biol Phys 2004;60(3):853-860

[36] Tsao MN, Mehta MP, Whelan TJ, et al The American Society for Therapeutic

Radiology and Oncology (ASTRO) evidence-based review of the role of

radiosurgery for malignant glioma Int J Radiat Oncol Biol Phys

2005;63(1):47-55

[37] Romanelli P, Conti A, Pontoriero A, et al Role of stereotactic radiosurgery and

fractionated stereotactic radiotherapy for the treatment of recurrent glioblastoma

multiforme Neurosurg Focus 2009;27(6):E8

[38] Laperriere NJ, Leung PM, McKenzie S, et al Randomized study of brachytherapy in

the initial management of patients with malignant astrocytoma Int J Radiat Oncol Biol Phys 1998;41(5):1005-1011

[39] Videtic GM, Gaspar LE, Zamorano L, et al Use of the RTOG recursive partitioning

analysis to validate the benefit of iodine-125 implants in the primary treatment of

malignant gliomas Int J Radiat Oncol Biol Phys 1999;45(3):687-692

[40] Selker RG, Shapiro WR, Burger P, et al The Brain Tumor Cooperative Group NIH Trial

87-01: a randomized comparison of surgery, external radiotherapy, and carmustine versus surgery, interstitial radiotherapy boost, external radiation therapy, and

carmustine Neurosurgery 2002;51(2):343-355; discussion 355-357

[41] Gaspar LE, Zamorano LJ, Shamsa F, et al Permanent 125iodine implants for recurrent

malignant gliomas Int J Radiat Oncol Biol Phys 1999;43(5):977-982

[42] Larson DA, Suplica JM, Chang SM, et al Permanent iodine 125 brachytherapy in

patients with progressive or recurrent glioblastoma multiforme Neuro-oncology

2004;6(2):119

[43] Patel S, Breneman JC, Warnick RE, et al Permanent iodine-125 interstitial implants for

the treatment of recurrent glioblastoma multiforme Neurosurgery

2000;46(5):1123-1128; discussion 1128-1130

[44] Keles GE, Lamborn KR, Chang SM, Prados MD, Berger MS Volume of residual disease

as a predictor of outcome in adult patients with recurrent supratentorial

glioblastomas multiforme who are undergoing chemotherapy J Neurosurg

2004;100(1):41-46

[45] Lawson HC, Sampath P, Bohan E, et al Interstitial chemotherapy for malignant

gliomas: the Johns Hopkins experience J Neurooncol 2006;83(1):61-70

[46] Valtonen S, Timonen U, Toivanen P, et al Interstitial chemotherapy with

carmustine-loaded polymers for high-grade gliomas: a randomized double-blind study

Neurosurgery 1997;41(1):44-48; discussion 48-49

[47] Westphal M, Ram Z, Riddle V, et al Gliadel® wafer in initial surgery for malignant

glioma: long-term follow-up of a multicenter controlled trial Acta Neurochir (Wien)

2006;148(3):269-275

[48] Silagy CA, Middleton P, Hopewell S Publishing Protocols of Systematic Reviews

JAMA: the journal of the American Medical Association 2002;287(21):2831

[49] Sarin H Recent progress towards development of effective systemic chemotherapy for

the treatment of malignant brain tumors J Transl Med 2009;7(1):77

[50] Roger M, Clavreul A, Venier-Julienne MC, et al The potential of combinations of

drug-loaded nanoparticle systems and adult stem cells for glioma therapy Biomaterials

2010

[51] Jain KK Use of nanoparticles for drug delivery in glioblastoma multiforme Expert Rev

Neurother 2007;7(4):363-372

[52] Jain KK Role of nanobiotechnology in the personalized management of glioblastoma

multiforme Nanomedicine (Lond) 2011;6(3):411-414

[53] Maier-Hauff K, Ulrich F, Nestler D, et al Efficacy and safety of intratumoral

thermotherapy using magnetic iron-oxide nanoparticles combined with external

beam radiotherapy on patients with recurrent glioblastoma multiforme J Neurooncol 2011;103(2):317-324

[54] Hickey MJ, Malone CC, Erickson KL, et al Cellular and vaccine therapeutic approaches

for gliomas J Transl Med 8:100-100

[55] Yamanaka R Dendritic-cell- and peptide-based vaccination strategies for glioma

Neurosurg Rev 2009;32(3):265-273

[56] Rainov NG, Kramm CM Recombinant retrovirus vectors for treatment of malignant

brain tumors Int Rev Neurobiol 2003;55:185-203

[57] Germano IM, Fable J, Gultekin SH, Silvers A Adenovirus/herpes simplex-thymidine

kinase/ganciclovir complex: preliminary results of a phase I trial in patients with

recurrent malignant gliomas J Neurooncol 2003;65(3):279-289

[58] Harrow S, Papanastassiou V, Harland J, et al HSV1716 injection into the brain adjacent

to tumour following surgical resection of high-grade glioma: safety data and

long-term survival Gene Ther 2004;11(22):1648-1658

[59] Singh SK, Clarke ID, Terasaki M, et al Identification of a cancer stem cell in human

brain tumors Cancer Res 2003;63(18):5821-5828

[60] Achanta P, Roman NI., Qui\ nones-Hinojosa A Gliomagenesis and the use of neural

stem cells in brain tumor treatment Anti-cancer agents in medicinal chemistry

2010;10(2):121

[61] Benedetti S, Pirola B, Pollo B, et al Gene therapy of experimental brain tumors using

neural progenitor cells Nat Med 2000;6(4):447-450

[62] Barresi V, Belluardo N, Sipione S, et al Transplantation of prodrug-converting

neural progenitor cells for brain tumor therapy Cancer Gene Ther

2003;10(5):396-402

[63] Tang Y, Shah K, Messerli SM, et al In vivo tracking of neural progenitor cell migration

to glioblastomas Hum Gene Ther 2003;14(13):1247-1254

EGFR and Glioma Therapy

Advances in the Development of EGFR Targeted Therapies for the Treatment of Glioblastoma

2 Expression of EGFR and its ligands in GBM

The EGFR is frequently expressed in GBM (Jungbluth et al., 2003), the most common and deadly form of malignant brain cancer (DeAngelis, 2001) Extensive co-expression of EGFR ligands such as EGF and TGF-α has also been reported (Ekstrand et al., 1991), suggesting the existence of a robust autocrine loop in many cases of GBM Furthermore, overexpression of the EGFR has been reported in up to 60% of GBM cases depending on the technique used (Libermann et al., 1985; Schlegel et al., 1994; Jungbluth et al., 2003), with overexpression leading to ligand-independent activation of the receptor (Thomas et al., 2003) The activation and subsequent phosphorylation of EGFR stimulates several downstream pathways including Ras/MAPK, PI3K/Akt, PLC-gamma and STAT3 (Halatsch et al., 2006; Nakamura, 2007) All four pathways contribute to the tumorigenicity of GBM, but the PI3K/Akt pathway appears to have a central role in the development and maintenance of this cancer (Chakravarti et al., 2004) Indeed, inactivation/deletion/mutation of PTEN, an endogenous inhibitor of the PI3K pathway, is also a common event in GBM (Rasheed et al., 1997) Of note, there is an emerging role for EGFR-mediated activation of STAT3 in the development

of GBM (Weissenberger et al., 2004; Mizoguchi et al., 2006; Sherry et al., 2009)

3 Amplification of the EGFR gene in GBM

Amplification of the EGFR gene was the first reported genetic alteration in GBM (Libermann

et al., 1985) Subsequent studies have confirmed that approximately 40% of GBMs display

amplification of the EGFR gene (Wong et al., 1987) Gene amplification invariably leads to

overexpression of the EGFR at the cell surface (Wong et al., 1987), although given that overexpression of the receptor occurs in 60% of GBMs, gene amplification is not the only route to increased expression The majority of GBMs develop rapidly, without evidence of

pre-existing malignant lesion, and are known as primary (or de novo) GBMs, while

secondary GBMs arise from low-grade diffuse astrocytomas or anaplastic astrocytomas

(Furnari et al., 2007; Ohgaki & Kleihues, 2007) EGFR gene amplification is more commonly

associated with primary GBMs than secondary GBMs, where it occurs at a frequency of less than 10% (Watanabe et al., 1996; Ohgaki & Kleihues, 2007) Overexpressed EGFR not only activates in a ligand-independent manner, but shows enhanced signaling through the STATs, including STAT3 (Thomas et al., 2003; Pedersen et al., 2005), which in turn can

induce expression of IL-6 Since IL-6 autocrine loops and amplification of the IL6 gene have

been reported at high frequency in GBM (Weissenberger et al., 2004; Tchirkov et al., 2007), this could be an important, but largely overlooked, consequence of EGFR overexpression Recent studies have shown that GBM can be classified into at least 4 distinct molecular sub-types; classical, pro-neural, neural and mesenchymal (Brennan et al., 2009; Verhaak et al., 2010) Pro-neural GBMs largely constitutes the secondary GBMs and therefore does not display EGFR amplification and/or overexpression In contrast nearly all GBM in the classical sub-type overexpress EGFR (Verhaak et al., 2010) Furthermore, the GBM specific mutation, de2-7 EGFR, is found almost exclusively in the classical sub-type Neural and mesenchymal GBMs have variable levels of EGFR with some showing increased expression and others decreased expression

4 Mutations of EGFR described in GBM

Amplification of the EGFR gene in GBM is associated with gene rearrangements The first

rearrangement to be described in detail was an extracellular domain (ECD) deletion producing a mutant known as the de2-7 EGFR (or EGFRvIII) (Sugawa et al., 1990; Yamazaki

et al., 1990; Ekstrand et al., 1992; Wong et al., 1992) Several other deletion mutants have since been described and categorized (Table 1) (Ekstrand et al., 1992; Frederick et al., 2000) Numerous subsequent studies have shown that the most common mutation is the de2-7

EGFR, occurring in about 50% of cases where the EGFR gene is amplified (Wikstrand et al.,

1998; Frederick et al., 2000; Pedersen et al., 2001) This cancer-specific EGFR mutant has a

specific deletion between exons 2 and 7 of EGFR (Sugawa et al., 1990) The truncation of

exons 2–7 leads to the elimination of 267 amino acids from the ECD and the insertion of a novel glycine at the fusion junction This renders the mutant EGFR unable to bind any known ligand (Sugawa et al., 1990; Wikstrand et al., 1998; Pedersen et al., 2001) Despite this, the de2-7 EGFR is capable of low-level constitutive signaling, which is augmented by the mutant receptor’s impaired internalization and downregulation (Nishikawa et al., 1994; Schmidt et al., 2003)

GBM cell lines transfected with the de2-7 EGFR display enhanced tumorigenicity when

grown as xenografts in nude mice, but only a marginal effect on growth is observed in vitro

(Nishikawa et al., 1994) Furthermore, expression of the de2-7 EGFR is consistently lost

when GBM cell lines are established in vitro using serum, yet is retained if GBM samples are

implanted and subsequently passaged directly in nude mice (Sarkaria et al., 2007) Taken

together, this indicates that the de2-7 EGFR contributes primarily to aspects of in vivo

growth While the increased tumorigenicity mediated by the de2-7 EGFR is primarily due to

the receptor’s constitutive tyrosine kinase activity (Huang et al., 1997), attempts to identify

intracellular molecules and signaling pathways associated with its growth advantage

remain ongoing Transfection of the de2-7 EGFR into U87MG human GBM cells results in an

increase in PI3K activity that is important to the growth advantage mediated by the mutant

receptor, an observation confirmed by several papers (Moscatello et al., 1998; Li et al., 2004;

Luwor et al., 2004) U87MG cells transfected with the de2-7 EGFR also co-express wild-type

(wt) EGFR, a scenario that probably mimics the situation in GBM patients The significance

of a possible interaction between the de2-7 EGFR and wtEGFR is not fully known, but it has

been shown that the de2-7 EGFR can directly activate PI3K in the absence of the wtEGFR in

non-GBM cell lines (Moscatello et al., 1998) We reported that the de2-7 EGFR and the wt

EGFR can heterodimerize leading to increased PI3K signaling (Luwor et al., 2004),

suggesting that an interaction between the mutant and wt receptor could enhance de2-7

EGFR signaling One clear consequence of PI3K activation by de2-7 EGFR is the increased

production of VEGF, both under normoxic and hypoxic conditions (Feldkamp et al., 1999),

ascribing a pro-angiogenic function to this receptor

Mutation Frequency (%) Biological Effect

Δ959–1030 but responds to ligand

responds to ligand

responds to ligand A265V/D/T <5 Increased basal activity but

responds to ligand

responds to ligand Kinase mutation (L861Q) <1 Increased basal activity, failure to

downregulate

Table 1 Selected mutations of the EGFR expressed in GBM

Very recently de2-7 EGFR has been shown to stimulate the production of cytokines,

including IL-6 and LIF, which signal through the gp130 complex (Inda et al., 2010)

Importantly these cytokines were shown to activate the wtEGFR when it is overexpressed in

neighboring GBM cells, through a mechanism involving cross-talk between gp130 and

EGFR Activation of the wtEGFR in this manner leads to enhanced proliferation Thus, de2-7 EGFR contributes to the growth of surrounding GBM cells through this field effect This work also shows the functional link between EGFR and IL-6 More generally this indicates that the de2-7 EGFR actively contributes to the heterogeneity of GBM by acting indirectly with neighboring de2-7 EGFR negative cells (Inda et al., 2010) This hypothesis is entirely consistent with the observation that wtEGFR amplification and de2-7 EGFR expression are usually seen together It may also explain why the pronounced growth advantage mediated

by the de2-7 EGFR does not lead in patients to a homogenous population of cells in patients all expressing the receptor

Lee et al sequenced the entire EGFR gene in a panel of eight GBM cell lines and 132 GBM

samples (Table 1) (Lee et al., 2006) Interestingly, they identified a series of missense mutations in the ECD of the EGFR expressed in 14% of the GBM samples and 12% of the cell lines (Lee et al., 2006) In general, the missense mutations were found to be independent of the

de2-7 EGFR but were associated with EGFR gene amplification; approximately 60% of samples with missense mutations also had EGFR gene amplification Subsequent studies showed that

these single amino acid mutations led to ligand-independent activation of the EGFR, and unlike the wtEGFR, were transforming in NR6 cells; a variant of mouse 3T3 cells lacking the EGFR (Lee et al., 2006) However, unlike the de2-7 EGFR, these mutants could also respond to ligand stimulation Recently, we extended these studies and showed that some of these

mutations also provide a significant advantage to in vivo growth (Ymer et al., 2011)

The presence of activating kinase mutations, such as those commonly found in lung cancer (Sharma et al., 2007), is extremely rare in GBM, with only one sample displaying this type of mutation (Lee et al., 2006) Interestingly, a subsequent analysis of 119 lung cancer samples failed to find a single missense mutation in the ECD, although 13% of the samples contained kinase domain mutations, as expected (Lee et al., 2006) Thus, mutations of the EGFR in GBM appear to cluster in the ECD and lead to ligand independence Therefore, the lessons learned with respect to EGFR therapeutics for the treatment of lung cancer are probably of minimal value in the context of GBM Finally, these mutations further emphasize just how frequently the EGFR is perturbed in GBM; in fact, taking into account EGFR autocrine loops, activation of the EGFR probably occurs in over 70% of GBMs

5 EGFR as a therapeutic target in GBM

Given that the EGFR is activated or dysregulated in a large percentage of GBM cases it is a rational target for therapeutic intervention in this disease There are two major classes of EGFR inhibitors either currently approved or being evaluated for the treatment of various cancers; antibodies that target the ECD and small molecule TKIs that target the intracellular kinase domain (Marshall, 2006) No specific agent from either class has been approved for the treatment of GBM, but as described below, a number of clinical trials have been reported

or are ongoing

5.1 Antibodies directed to the EGFR

Overexpression of the de2-7 EGFR on the cell surface, the unique junctional peptide created

by the deletion and the aggressive phenotype associated with this receptor, suggests that targeting the de2-7 EGFR with antibodies that are cancer-specific is an attractive therapeutic